#include <fstream>
#include <vector>

using namespace std;

ifstream f("amenzi.in");
ofstream g("amenzi.out");

const int NMAX = 153;
const int TMAX = 3503;
const int inf = 0x3f3f3f3f;

int n,m,k,p,A[TMAX][NMAX],c[NMAX][NMAX],amenda[TMAX][NMAX],a,b,cs,x,y,i,j,t,t1;
vector <int> v[NMAX];

int maxim(int a, int b)
{
    if(a>b) return a;
    return b;
}

int main()
{
    f>>n>>m>>k>>p;
    for (i=1;i<=m;i++)
    {
        f>>x>>y;
        f>>c[x][y];
        c[y][x]=c[x][y];
        v[x].push_back(y);
        v[y].push_back(x);
    }
    for (i=1;i<=k;i++)
    {
        f>>a>>b>>cs;
        amenda[b][a]+=cs;
    }

    for (t=0;t<TMAX;t++)
    {
        for (x=1;x<=n;x++)
        {
            A[t][x]=-inf;
        }
    }

    A[0][1]=0;

    for (t=1;t<TMAX;t++)
    {
        for (i=1;i<=n;i++)
        {
            for (j=0;j<v[i].size();j++)
            {
                x=v[i][j];
                t1=t-c[i][x];
                if (t1<0)
                    continue;
                A[t][i]=maxim(A[t][i],A[t1][x]);
            }
            A[t][i]=maxim(A[t][i],A[t-1][i]);
            if (A[t][i]!=-inf)
            {
                A[t][i]+=amenda[t][i];
            }
        }
    }

    for (i=1;i<=p;i++)
    {
        f>>a>>b;
        if (A[b][a]!=-inf)
        {
            g<<A[b][a]<<'\n';
        }
        else g<<"0"<<'\n';
    }

    f.close();
    g.close();
    return 0;
}